1. Field of the Invention
The present invention relates to electrophoresis, and more particularly, to the structure of the electrolyte tank of an electrophoretic system.
2. Description of the Related Arts
Electrophoresis is a technique by which articles such as mixtures of macromolecules are moved through a separation medium by an electric field. It is a widely used technique for quantitative analysis and for separation, recovery and purification of certain macromolecular species. It is widely used for the study of proteins, nucleic acids and chromosomes.
U.S. Pat. No. 4,740,283 to Laas et al is incorporated by reference herein. The patent describes a transverse alternating field gel electrophoretic system in which a free-standing gel slab is subject to alternating electric fields oriented diagonally across the thickness of the gel slab. The alternating fields are oriented at angle ("reorientation angle") with respect to each other and cause the molecules to migrate down the gel slab in a generally saw-tooth manner oscillating within the thickness of the gel slab. The amount of migration is determined in part by the electrical charges on the particles in the sample substance, the size of the particles and the magnitude of the imposed electrical potential. Particles with similar mobilities tend to group into defined areas and thus a determination can be made as to the relative sizes of each group of particles present in the sample. At the end of the separation process, groups of particles of different mobilities are aligned along the path of migration i.e. separation lanes of the particles. Typically, several samples are processed at the same time thus forming several separation lanes in the gel slab.
The theory behind transverse alternating field electrophoresis is that separation of the sample particles can be achieved by reorientation of the particles as they migrate down the gel slab, smaller particles being able to reorient themselves faster than larger particles. Reorientation occurs each time the electric field is switched between the two transverse pairs of electrodes. It has been found that transverse alternating fields result in better resolution especially in the separation of large DNA fragments greater than 50,000 base pairs.
It has been found that the reorientation angle, defined by the angle between the original direction of migration in one instance and the reoriented direction in the next instance, i.e. the angle between the transverse directions of the alternating fields, can affect the separation efficiency. Since the migrations of the particles follow the electric field, the placement of the electrodes with respect to the gel slab can have a significant effect on the reorientation angle and thus the efficiency of the electrophoretic separation.